[antlr-interest] Switching between different lexers from within parser

Helmut Neukirchen neukirchen at itm.mu-luebeck.de
Wed Jan 23 08:30:25 PST 2002

Hi folks,

is there a possibility to switch in a clean and deterministic way
beetween different lexers from within the *parser*? 

In contrast to the Javadoc example, where switching between different
lexers is done from within the lexers, I have to deal with a language 
where this is only possible from within the parser.
(Think e.g. of C with embedded SQL, but without the leading "EXEC SQL" 
which usually introduces each statement of embedded SQL.)

In my language, the parser is the only instance which is able to decide
which lexer has to be chosen next. On the other hand, due to the look-ahead 
and the loose coupling between parser and lexers through the token stream, 
the wrong lexer might already have scanned and consumed characters which 
were in fact intended for the other lexer.

Any ideas?

Helmut Neukirchen                   mailto:neukirchen at itm.mu-luebeck.de
Institute for Telematics                   http://www.itm.mu-luebeck.de
Medical University of Luebeck                   phone: +49 451 500 4867
Ratzeburger Allee 160, D-23538 Luebeck, Germany   fax: +49 451 500 3722


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